1. Field of the Invention
The present invention relates to a process for thickening a drilling mud waste materials whereby the drilling mud waste materials may be optionally safely transported and disposed to another area, such as for example but not limited to a landfill. In particular, this invention provides such a process wherein the aqueous drilling mud waste materials (effluent from the drilling process) is thickened by mixing it with an effective amount of an anionic copolymer to form a treated drilling mud waste materials. The treated drilling mud waste materials are then optionally transported for disposal to another location, such as a landfill.
2. Background Art
In the oil and gas industries, drilling processes produce waste streams that are associated with oil and gas operations. Drill site construction and rigging produce debris as well as drilling activities which include for example but are not limited to operation of the rig, and use of a drilling mud system, drill cuttings, spent and used solvents, paint and paint wastes, pipe doping materials, sand and scale, paraffin, and hydraulic fluids, all of which may contaminate soil. Drilling fluid (i.e. “drilling mud”) is used to maintain hydrostatic pressure for well control, carry drill cuttings to the surface, and cool and lubricate the drilling bit. These drilling muds may be fresh water based, salt water based, oil based, or synthetic. These waste materials and waste streams are frequently diverted to a drilling mud waste pit that must be contained and further processed so that the wastes may be properly disposed of. The treatment of the drilling mud waste pit is time consuming and costly. Current environmental regulations require that waste materials for disposal into landfills must pass a paint filter liquid test, as described herein. The paint filter liquid test when performed on a representative sample of the waste materials is determinative of whether the subject waste material is deemed to be free of any free liquids and therefore acceptable for disposal in a landfill.
U.S. Pat. No. 4,063,386 teaches a method for restoring of drilling mud pits comprising the covering of the floc in a mud pit with a dry material capable of absorbing water from the floc and covering the material with earth. U.S. Pat. No. 4,063,386 discloses that the absorbent material is a natural cellulosic material that is saw dust, wood chips, peat, cork, straw, corncobs, leaves, or paper waste materials. U.S. Pat. No. 4,063,386 also discloses that the absorbent material may be chips of foam of polyurethane, polystyrene, polyethylene, or polypropylene. U.S. Pat. No. 4,063,386 teaches that the quantity of absorbent material used is such that it can absorb all of the water from the floc of the mud pit.
U.S. Pat. No. 4,353,803 teaches a flocculant useful for waste drilling fluid reserve pit treating wherein the reserve pit contains an aqueous spent oil-well drilling mud including an anionic colloid selected from the group consisting of drilling-fluid grade lignosulfonate and alkaline-soluble lignite, the flocculant consisting essentially of from 24 to 49 parts by weight of aluminum sulfate per part by weight of polyacrylamide homo-polymer having from 130 to 500 pendant amide groups per pendant carboxylic-acid or carboxylic-acid-salt group and having a molecular weight in the range of from 10,000 to 5 million. U.S. Pat. No. 4,353,803 teaches a process of separating into good quality water and high density solids, an admixture of waste drill cuttings, drilling fluid and by-products of rotary drilling, which process comprises combining the aluminum sulfate and polyacrylamide homo-polymer flocculant with the admixture, flocculating solids in the admixture and separating water from the flocculated solids within a few days.
U.S. Pat. No. 4,913,585 teaches treating a waste drilling mud by flocculating, aggregating, agglomerating and dewatering the waste drilling mud and separating out free water. The process disclosed in U.S. Pat. No. 4,913,585 stabilizes the waste drilling mud for earthern burial. U.S. Pat. No. 4,913,585 discloses that the thickened, dewatered drilling mud solids may be further treated with a water absorbing binder to produce a residue which has sufficient bearing strength to support an earthen overburden and may be disposed of by burial. U.S. Pat. No. 4,913,585 discloses that the water absorbing binder may be natural gums (e.g., carboxymethylcellulose, guar, hydroxyethylcellulose, carrageenan, alginates, and low to moderate molecular weight polyacrylamide polymers). U.S. Pat. No. 4,913,585 teaches the addition of a gallon of polyacrylamide emulsion to a barrel of separated sludge having a solids content of approximately 20-35% by volume. The combined sludge and polyacrylamide emulsion are mixed, and bagged and sealed in plastic bags for transport to a landfill. U.S. Pat. No. 4,913,585 further teaches that a separated drilling mud waste sludge may be further treated by applying a water permeable layer such as sand, for example, four inches in thickness over the top of the separated waste sludge, and that a polyacrylamide absorbent binder layer of approximately one-sixth of an inch thickness is placed above the sand layer, and that about four feet of an earth overburdern may be placed on top of the polyacrylamide absorbent binder layer. U.S. Pat. No. 4,913,585 states that the overlying earthen overburden, water absorbent polyacrylamide layer, and sand compress the sludge so that a portion of the remaining moisture content is squeezed out of the sludge and percolates up through the sand layer and into the water absorbent binder layer (acrylamide layer). U.S. Pat. No. 4,913,585 states that the water absorbent binder (acrylamide layer) remains separated from the waste drilling mud solids. It is believed that under the current environmental landfill regulations, waste sludge treated according to the teachings of U.S. Pat. No. 4,913,585 would fail the paint filter liquids test.
It is known to add fly ash as a thickener to aqueous drilling mud waste materials. However, doing so has the disadvantage of requiring addition of 2 parts fly ash to every 1 part drilling mud waste. It is known to add sawdust as a thickener to drilling mud waste materials. However, doing so has the disadvantage of requiring 3 parts sawdust to every 1 part of drilling mud waste materials. One-half of the weight of the resulting treated solid is sawdust. It is know by those skilled in the art to add wood chips as a thickener to drilling mud waste materials but the wood chips require even a higher ratio of woods chips to drilling mud waste materials compared to sawdust addition since the wood chips have a lower absorptive capacity than sawdust. Thus, wood chips as a thickener possess even a greater disadvantage than use of sawdust. Quick lime is known to be used as a thickener added to drilling mud waste materials but such addition requires greater than 4 parts quick lime to 1 part drilling mud waste materials and such addition has the further disadvantage of generating heat that can be hazardous. It is known to use the sodium salt of polyacrylic acid to thicken drilling mud waste materials however the absorptive capacity of the sodium salt of polyacrylic acid is one-third that of the potassium salt of the cross-linked copolymer and is not economical.
Up to now, the known absorbing processes and dewatering processes utilized in drilling mud waste pit restoration have been time consuming and expensive. The treated mud waste pit must pass a paint filter liquids test that is used by landfills to determine acceptability of the treated drilling wastes prior to its disposal. The present applicants have developed such a process that advantageously provides for the thickening of the aqueous and non-aqueous fluids of a drilling mud waste materials such that the treated waste may be transported from the drilling site to a landfill within several hours of treatment.
The present applicants have found unexpected results with the process of the instant invention in that the present applicants are able to (1) thicken the drilling mud pit waste materials such that the liquid content of the treated waste is tied up so as to pass the landfill disposal tests, (2) apply the superabsorbent anionic copolymer of the instant process with the use of mechanical means, (3) achieve a reaction and solidification time from an hour to less than twelve hours of treating the drilling mud waste materials; and (4) to effect a minimal change in the overall volume of the pre-treated drilling mud waste materials compared to the volume of the treated drilling mud waste materials. Thus, the applicants process provides the added economic benefits of thickening the drilling mud waste materials while not substantially increasing the volume of treated waste that requires transportation to a landfill compared to the use of known combinations of additives that reduce the liquid water content of the waste but increase the volume of the treated waste for transportation by several fold. Thus, applicants process fulfills a long-felt but heretofore unmet need in the oil and gas industry for processing drilling mud waste materials and for restoring the land where the drilling mud waste pit is physically located.